The present invention relates to a guidewire for guiding a medical device having a hollow structure such as a catheter or the like, which is introduced into a human body directly or through an endoscope in a medical treatment or inspection.
In recent years, medical treatments have come to introduce positively a technique which makes less incision damages to a human body. Specifically, in place of an incision operation, such as abdominal section, thoracotomy or the like, which provides a heavy physical burden to a patient, an inspection and a treatment carried out by inserting various catheters into a human cavity have come to be used. In case of practicing such a technique, it is general that a guidewire is inserted through a catheter which is to be inserted into a human body and a device such as the catheter or the like is guided to an aimed body cavity portion along the guidewire. Many guidewires of this kind are used in an inspection or a treatment on a stomach, duodenum, bile duct, cholecyst, liver, pancreatic duct, pancreas, or the like, as a digestive organ.
Conventional guidewires for digestive organs, used with the technique of such a low incision damage, are suggested in Japanese Patent Application KOKAI Publication No. 2-180277 and U.S. Pat. No. 5,111,829, for example. Each of these guidewires has an inner core made of a superelastic metal and an X-ray contrast portion provided at the top end, and the entire of the inner core and the X-ray contrast portion is coated with a synthetic resin. The coating has a substantially uniform outer diameter and has an outer circumferential surface which is shaped into a smooth and even cylindrical surface without roughness.
However, in the guidewires described above, the outer circumferential surface of synthetic resin coating the inner core has a smooth cylindrical shape without roughness. Therefore, in case of actually guiding a catheter by the guidewire described above, the inner circumferential surface of the catheter is closely contacted on and intensively sticks to the smooth and even outer circumferential surface of the guidewire. The friction resistance when the guidewire slides is large and makes worce an operability in inserting and/or pulling out a catheter.
In this respect, Japanese Utility Model Application KOKOKU Publication No. 2-40992, Japanese Patent Application KOKAI Publication No. 62-231675, Japanese Utility Model KOKOKU Publication No. 61-7735, and U.S. Pat. No. 4,579,127 have proposed guidewires each of which has an outer circumferential surface formed in an uneven shape in order to decrease the friction resistance to a catheter or the like.
In the guidewire suggested in Japanese Utility Model Application KOKOKU Publication No. 2-40992, a tube-like member freely engaged on the inner core is formed of a net-like member or the outer circumferential surface of the tube-like member is processed by a lacquer ware with a flecked effect, so that the outer circumferential surface of the tube-like member is formed to have an uneven surface.
In the guidewire according to Japanese Patent Application KOKAI Publication No. 62-231675, a thin wire-like inner core is coated with a relatively thick coating layer, and the outer circumferential surface portion of the coating layer is formed to be uneven.
In the guidewire according to Japanese Utility Model Application KOKOKU Publication No. 61-7735, a relatively thin coating film is applied to the outer circumference of the coil-like spring composing the guidewire, such that the coating film has an uneven shape.
U.S. Pat. No. 4,579,127 suggests a catheter and a probe-mandrel, which are comprised of a wire core and an external wire wound like a coil on the wire core, and a thin resin-made coating layer of a uniform thickness is formed on the semicircular circumferential surface.
The guidewire according to Japanese Utility Model Application KOKOKU Publication No. 2-40992 is made of a tube-like member freely engaged on an inner core and has a drawback that the structure is complicated and thick. Although its thickness, its rigidity is rather low, and further, the guidewire lacks a force transmission ability when it is twisted.
In the guidewire according to Japanese Patent Application KOKAI Publication No. 62-231675, its narrow wire-like inner core is coated with a relatively thick coating layer, so that the guidewire tends to be thickened with ease. The rigidity of the guidewire is rather low in spite of its thickness. Further, the guidewire lacks a force transmission ability when it is twisted. In the guidewire according to Japanese Utility Model Application KOKOKU Publication No. 61-7735, it comprises a coil-like spring as a core member, so that the guidewire lacks rigidity and a force transmission ability when it is twisted. Further and the follow-up ability of its top end portion is low.
Further, the mandrel according to U.S. Pat. No. 4,579,127 has a structure in which an external wire is wound like a coil on the wire core, so that the guidewire has low rigidity although it has flexibility, and the guidewire lacks force transmission ability when it is twisted. In this structure, the function of guiding a catheter or the like easily tends to be affected. Also, the entire guidewire must be thickened to improve the rigidity and the transmission ability. However, such a guidewire is not preferable as a guidewire.